The sites below have a lot of detailed information about the Ridge Route and its history.
- RidgeRoute.Com by Harrison Scott – Covers the history of the route and has books for sale
- Historic Highway 99 Association of California
- Virtual Tour of the Ridge Route by Michael Ballard – Online tour of the highway from Castaic to Gorman
- Virtual Tour of US 99 by Michael Ballard – Online tour of the highway from Los Angeles to Famoso
- That Ribbon of Highway by Jill Livingston – Books on US 99 along its entire length
- National Register of Historic Places – Ridge Route Listing
- Ridge Route Communities Museum – Information on the history of the area north of Castaic as well as the Ridge Route